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Why Won’t My Car Start with a Jump? 6 Main Reasons

By Aminah

Why Won't My Car Start with a Jump

As an electrical engineer, I love explaining how things like circuits and electronics work. I write on my blog to share simple explanations, reviews, and useful tips about the latest technology.

Nothing is more frustrating than turning the key in your car's ignition and hearing silence. A jump start can often provide a quick solution if your car won't start. However, there are instances where even a jump start won't get your vehicle going. You should learn the answer to “why won't my car start with a jump?” As an expert technician, I will tell you some possible reasons with solution. In order to save money, you need to access the system yourself before calling a technician.

If your car won't start even with a jump, you might have a serious problem. It could be a faulty battery, a bad alternator, or a damaged starter. You need to find out the cause and fix it as soon as possible, or you could end up stranded on the road.

How to Troubleshoot a Car That Won't Start with a Jump?

How to Troubleshoot a Car That Won't Start with a Jump

While a jump start can often breathe life back into a dead car battery, it doesn't guarantee your vehicle will start. If you find yourself in a situation where your car won't start even after a jump, you'll need to troubleshoot the problem systematically. This involves checking various components and systems to identify the root cause. There are some common causes of a car not starting with a jump and how to address them.

Why Won't My Car Start with a Jump | Common Causes of a Car Not Starting with a Jump

Jump-starting a car is a common method used to start a vehicle with a dead battery by using the power from another vehicle's battery. However, there are several reasons why a car may not start even after attempting a jump start. So, why won't my car start with a jump. Here are some common causes:

1. Old Or Dead Battery

A dead or severely discharged battery is the most common reason a car won't start. If your battery doesn't have enough power to crank the engine, even a jump start may not provide sufficient energy to get it going.

Why Won't My Car Start with a Jump

Solution: In most cases, replacing the dead battery is the best solution. If you don't have access to a replacement battery, you can attempt to recharge the dead one using a battery charger, which may take some time.

2. Damaged Jumper Cables

The effectiveness of a jump start depends on the quality and condition of the jumper cables used. Damaged or poorly functioning jumper cables may not transfer enough power to start the dead vehicle.

Sign of faulty jumper cables

Solution: Ensure you use high-quality, undamaged jumper cables with sufficient gauge (thickness) to carry the required current. If your cables are damaged, replace them.

3. Loose or Corroded Battery Terminals

Corroded or loose battery terminals can inhibit the flow of electrical current between the battery and the starter motor, preventing the engine from cranking.

How to fix Loose or Corroded Battery Terminals

Solution: Check the battery terminals for corrosion and tightness. If they are corrupted, clean them with a battery terminal cleaner or a mixture of baking soda and water. Tighten any loose connections.

4. Faulty Engine Compression

If your car's engine doesn't have sufficient compression, it may not start, even with a jump. Worn piston rings, damaged valves, or a blown head gasket can cause engine compression problems.

How to fix Faulty Engine Compression

Solution: Diagnosing and repairing engine compression problems is a complex task best left to professional mechanics. If you suspect engine compression issues, consult a mechanic for a thorough diagnosis.

5. Faulty MAF Sensor

The Mass Airflow (MAF) sensor measures the air entering the engine and adjusts the fuel injection accordingly. A faulty MAF sensor can disrupt the air-fuel mixture and prevent the engine from starting.

How to fix Faulty MAF Sensor

Solution: If you suspect a faulty MAF sensor, have it inspected and replaced by a qualified mechanic. They can use diagnostic tools to confirm the sensor's condition.

6. Damaged Crankshaft Position Sensor

The crankshaft position sensor monitors the position and speed of the crankshaft. It provides critical information to the engine control unit (ECU) to synchronize fuel injection and ignition timing. A faulty crankshaft position sensor can result in a no-start condition.

How to fix Faulty Crankshaft Position Sensor

Solution: Diagnosing and replacing a faulty crankshaft position sensor requires specialized equipment and knowledge. Seek assistance from a mechanic for proper diagnosis and repair.


How Long Does a Dead Battery Take to Jump?

The time it takes to jump-start a dead battery can vary depending on several factors, including:

1-Battery State: The dead battery's depletion level plays a significant role. A moderately discharged battery may start within 5-10 minutes, while a completely dead battery might require more time to accept a charge.

2-Battery Capacity: Batteries come in different capacities (measured in ampere-hours, Ah). A higher-capacity battery usually between 60 Ah and 90 Ah can take longer to charge fully.

3-Charging Current: The output capacity of the good battery and the alternator of the running vehicle also affects charging time. A higher-output alternator can charge the dead battery more quickly.

4-Environmental Conditions: Extremely cold or hot temperatures can affect the efficiency of the charging process. Cold weather, in particular, can slow down the chemical reactions inside the battery.

5-Battery Age and Condition: The age and overall condition of the dead battery play a role. 5+ Years older or worn-out batteries may require more time to charge, and in some cases, they may not hold a charge.

In general, allowing the dead battery to receive a charge for at least 5 to 10 minutes before attempting to start the vehicle is advisable. If the vehicle doesn't start after this time, it may require additional charging or the replacement of the dead battery.


How to Jump Start a Completely Dead Battery? Step BY Step Guide

A dead battery can leave you stranded and frustrated, but with the right equipment and knowledge, you can safely jump-start your vehicle and get back on the road.

Gather the Necessary Tools and Materials

Before attempting to jump-start a completely dead battery, ensure you have the following tools and materials:

  • Jumper Cables: Use heavy-duty jumper cables with thick gauge wires to ensure proper electrical conductivity.
  • Another Vehicle with a Good Battery: You'll need a vehicle with a fully charged battery to provide the jump start.
  • Safety Gear: Wear safety glasses and gloves to protect yourself from any potential sparks or battery acid.
  • Owner's Manual: Consult your vehicle for specific jump-starting instructions or precautions.

Ensure Safety

Safety should be your top priority when dealing with dead batteries and jump-starting. Follow these safety precautions:

  • Park both vehicles safely, ensuring they are not in the traffic path.
  • Turn off both vehicles' ignition and all electrical accessories (lights, radio, air conditioning).
  • Keep open flames and cigarettes away from the battery.
  • Do not allow the jumper cable clamps to touch each other while connected to a battery.
  • Always connect the cables correctly: positive to positive and negative to negative.

Identify Battery Terminals

Before connecting jumper cables, identify both batteries' positive (+) and negative (-) terminals. The positive terminal is usually marked with a "+" sign or a red cap, while the negative terminal is marked with a "-" or black cap.

Connect the Jumper Cables

Follow these steps to connect the jumper cables:

Step 1: Connect Positive to Dead Battery

Attach one end of the red (positive) jumper cable to the positive terminal of the completely dead battery. Attach the other end of the red jumper cable to the positive terminal of the good battery. Attach one end of the black (negative) jumper cable to the good battery's negative terminal.

Step 2: Connect Negative to Chassis Ground

Instead of connecting the other end of the black jumper cable to the negative terminal of the completely dead battery, find an unpainted, metallic part of the engine block or chassis away from the battery. 

This serves as a "chassis ground" and helps reduce the risk of sparking near the potentially hydrogen-rich area around the dead battery. Once you've identified a suitable chassis ground, securely attach the black jumper cable clamp.

Step 3: Start the Engine

With the cables properly connected, start the engine with a good battery and let it run for a few minutes. This allows the dead battery to receive a charge. After 5-7 minutes, try to start the vehicle with the dead battery. If it starts successfully, leave both engines running for a few more minutes to ensure the dead battery receives a sufficient charge.

Step 4: Disconnect the Jumper Cables

When you're confident that the dead battery has received enough charge, follow these steps to disconnect the jumper cables:

  • Begin by removing the black (negative) jumper cable from the chassis ground of the vehicle with the dead battery.
  • Next, remove the black jumper cable's other end from the good battery's negative terminal.

Step 5: Disconnect Positive from Good Battery

Remove the red (positive) jumper cable from the positive terminal of the good battery. Finally, remove the red jumper cable's remaining end from the dead battery's positive terminal. Now you know the answer - why won't my car start with a jump?

In such cases, it's crucial to systematically approach troubleshooting, starting with the most common causes and working through potential issues. If you're uncertain about the problem or lack the tools and expertise to diagnose and repair it, it's wise to seek the assistance of a qualified mechanic


Conclusion

While jump-starting a car is a handy way to get it going when the battery is dead, it's essential to recognize that not all no-start situations can be resolved with a jump start alone.

Suppose your car refuses to start even after a jump. In that case, the issue may lie deeper within the vehicle's systems, such as a faulty sensor, engine compression problems, or other mechanical issues. I hope now you know “why won't my car start with a jump?”